docs: def _extract_colnum(self, col):
          """
          Get the column number for the input column
          """
          if isinteger(col):
              colnum = col
  
              if (colnum < 0) or (colnum > (self._ncol-1)):
                  raise ValueError(
                      "column number should be in [0,%d]" % (0, self._ncol-1))
          else:
              colstr = mks(col)
              try:
                  if self.case_sensitive:
                      mess = "column name '%s' not found (case sensitive)" % col
                      colnum = self._colnames.index(colstr)
                  else:
                      mess \
                          = "column name '%s' not found (case insensitive)" % col
                      colnum = self._colnames_lower.index(colstr.lower())
              except ValueError:
                  raise ValueError(mess)
          return int(colnum)